This video demonstrates a fast AK-47 magazine change technique. The video author calls it the “Shayetet 13 style”. Shayetet 13 are an elite IDF marine special forces unit, similar to the SEALs. I would be surprised if they were the sole inventors of this technique, it was more likely simultaneously discovered by AK-47 wielding soldiers around the world.
Remember, this technique is for emergencys only, doing it repeatedly could wreck your magazines.
UPDATE: I posted the wrong video. The video above is now the correct video.
Hat Tip: FromanMD @ MP.net